In situ rechargeable battery and charging stand

ABSTRACT

A secondary button cell battery that is particularly suited for use in hearing aid appliances, and an associated charging station. Recharging is accomplished without direct conductive connection between the source of the energy and either the battery or its appliance. Radio frequency energy is harvested in an enclosed chamber in a charging station and applied to the recharging of the button cell. Such energy is harvested by the use of one or more energy harvesting diodes connected in parallel with the battery. Multiple diodes connected in parallel or serial may be used to adjust charging current or voltage or both. Charge control is provided by directly or indirectly detecting the level of charge on the cell. Where the associated appliance is a hearing aid, the charge level detection may be accomplished acoustically by determining the characteristics of the sound emitted by the hearing aid, and charging is accomplished with the cell within the hearing aid appliance.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/516,205, filed Oct. 31, 2003. This application is a division ofU.S. application Ser. No. 10/976,490, Filed Oct. 29, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to methods and devices for smallsecondary batteries and the recharging thereof, and in particular,rechargeable hearing aid batteries and recharging appliances therefor.

2. Description of the Prior Art

As is well known in the fields where small batteries are used to powerelectronic devices, and in particular in the hearing aid field,secondary batteries require periodic recharging and primary batteriesrequire frequent replacement. Previous primary batteries typicallylasted no more than, for example, approximately one week in hearing aidappliances. Such replacement of primary batteries requires physicalmanipulation of the small batteries. However, those hearing-impairedpersons needing an aid are often afflicted with arthritis or otherailments and may have trouble manipulating the small rounded batteryinto the case. In addition, many hearing aid wearers and other usersoften forget to purchase batteries, or find it inconvenient to go out toobtain them. Primary batteries also represent an ongoing expense, andmany hearing-impaired persons, for example, are required to live on arather stringent budget.

The use of a rechargeable cell or battery in a hearing aid device isknown, but such previous expedients suffered from several shortcomings,and have generally not solved the above-mentioned problemssatisfactorily. Previous secondary hearing aid batteries lackedsufficient energy density and thus could not power the hearing aid foran adequate length of time. Such previous secondary batteries with shortdischarge cycles were generally unsatisfactory. Also, the expense ofsuch secondary batteries was prohibitive for many users.

Two types of rechargeable hearing aids had been previously proposed. Thedirect plug-in type required the wearer to plug a charger directly intoa socket on the hearing aid, to apply recharging current directly to thebattery. The inductively rechargeable type of hearing aid was simplydropped, battery and all, into a recharger appliance, which produced analternating current magnetic field. This oscillating field was convertedby appropriate circuitry in the hearing aid itself, into a directcurrent that recharged the hearing aid battery. These types ofrechargeable aids and associated charging stations, are specializeddevices that can not be used with a standard unmodified hearing aid. Astandard hearing aid cannot be plugged in or inductively charged withsuch previous expedients. It would be of great benefit if high energydensity secondary batteries mounted in conventional unmodified hearingaids could be remotely recharged either by induction or by radiofrequency (RF) energy, or the like. The provision of secondary batteriesthat include recharging electronics within the battery would furtherbenefit the art. The utility of a secondary hearing aid battery with aconventional unmodified hearing aid could be greatly enhanced by theprovision of a recharging station where no handling of the batteryoutside of the hearing aid is necessary.

These and other difficulties of the prior art have been overcomeaccording to the present invention.

BRIEF SUMMARY OF THE INVENTION

The present invention has been developed in response to the currentstate of the art, and in particular, in response to these and otherproblems and needs that have not been fully or completely solved bycurrently available expedients. Thus, it is an overall object of thepresent invention to effectively resolve at least the problems andshortcomings identified herein. In particular, it is an object of thepresent invention to provide a small secondary battery, for example, arechargeable hearing aid battery, with recharging electronicsincorporated therein, which secondary battery can be used with aconventional unmodified appliance, for example, a hearing aid. It isalso an object of the present invention to provide a charging stationinto which the entire unmodified appliance with the battery in place canbe placed without further manipulation. It is a further object of thepresent invention to provide such a secondary battery and associatedcharging station wherein charging can be accomplished by radiofrequency, inductive charging, transducer received charging, or thelike, and without modifying the associated appliance. Embodiments of thepresent invention are particularly suitable for use with a conventionalhearing aid.

To acquaint persons skilled in the pertinent arts most closely relatedto the present invention, a preferred embodiment of a secondary battery(a button cell) and associated charging station for a conventionalunmodified hearing aid that illustrates the best mode now contemplatedfor putting the invention into practice is described herein by, and withreference to, the annexed drawings that form a part of thespecification. The exemplary assembly is described in detail withoutattempting to show all of the various forms and modifications in whichthe invention might be embodied. As such, the embodiments shown anddescribed herein are illustrative, and as will become apparent to thoseskilled in the arts, can be modified in numerous ways within the scopeand spirit of the invention, the invention being measured by theappended claims and not by the details of the specification or drawings.

The present invention includes a small secondary button cell batteryhaving a chemistry that is appropriate to the intended use, a caseconfiguration that tends to resiliently compress the battery chemistryat all times during the discharge-recharge cycle, a flexibly configuredseparator, and a self contained recharging circuit. The structuralelements of the button cell (case and separator) are all recoverablydeformable to accommodate the volumetric changes that inherently occurduring the discharge-recharge cycle of an electrochemical cell withoutsuffering permanent deflection or distortion. In one preferredembodiment the recharging circuit can be, for example, one or moreenergy harvesting diodes. Charge control is provided by directly orindirectly detecting the level of charge on the battery and controllingthe amount of applied charging energy in response to the detected chargelevel. A recharging station is also provided according to the presentinvention. The recharging station is adapted to recharging the batterywhile it is in operative association with an electronic appliancewithout electrically conductive contact between the recharging stationand either the battery or the appliance in which it is mounted. Havingall of the recharging circuitry in the battery itself providessignificant cost, reliability, and convenience benefits. Once installed,a rechargeable battery according to the present invention, particularlya button battery, generally need not be removed from the associatedappliance for the life of the rechargeable battery. Because the batterycan be recharged numerous times, the battery need not be removed orhandled for extended periods of time, for example, in a conventionalhearing aid appliance. This is a significant improvement in convenienceand cost over the present widely used non-rechargeable button batterythat must be replaced about once a week. Additional convenience andsafety are afforded by the present invention as against the use ofprevious expedients. For instance, in previous expedients the batterydoor of an appliance, for example, a hearing aid appliance, had to beopened when the hearing aid was not being worn. This was done to turnoff the hearing aid. This conserved battery energy and silenced theacoustic feedback “squeal” that is typically emitted from a hearing aidwhen it is not being worn. Unfortunately, when the battery door wasopened, the battery had a tendency to fall out of the appliance. Becauseof its small size and round wheel like shape, when the battery fell outit tended to roll. In many instances, the dropped battery was lost.

According to the present invention, these and other difficulties ofpreviously proposed expedients are eliminated. According to the presentinvention the recharging station can be configured to automatically turnoff the electronic appliance every time it is placed on the rechargingstation, or to utilize the “on” stage of the appliance as part of thecharge control during the recharging phase of the discharge-rechargecycle. Generally, it is preferred to employ a recharging station that isconductively connected to the conventional house current that isgenerally available in the area. Portable battery powered rechargingstations, however, have some utility. If the user wishes to turn off theappliance when a regular recharging station is not readily at hand, theappliance can be placed temporarily in a portable battery operatedpocket sized recharger. By so doing, the appliance can be, for example,turned off and the battery can be “topped off” thus giving it an evenlonger period of use before it requires an extended recharging.

The long battery life cycle according to the present invention permitsthe provision of yet another option to a user who wishes to turn off theelectronic appliance. A user can turn off the appliance by opening thebattery door without risk that the battery will fall out of theappliance if an adhesive is employed to mount the battery in the batterycompartment of the appliance. It is possible to adhesively secure thebutton battery in operative configuration with the appliance because thebattery does not have to be replaced but approximately once a year.

A wide variety of secondary battery chemistries can be utilized,including, for example zinc/silver oxide, nickel/metal hydride,rechargeable lithium chemistries, nickel/cadmium, iron/nickel oxide,cadmium/silver oxide, zinc/nickel oxide, lead-acid, and the like. Manysuch systems and their characteristics are known to those skilled in theart. The present invention is not limited to any particular secondarybattery chemistry. The battery chemistry can be tailored to theparticular requirements of the associated appliance. Safe andenvironmentally friendly electro-chemical reactants can be employed ifdesired.

Other charging arrangements can be provided, for example, hearing aidshave transducers for picking up sound. Acoustic energy can be harvestedthrough the transducer to provide alternating current. The alternatingcurrent can be converted to direct current (rectified), and applied tocharging the secondary battery.

The system can be switched on and off by many means, including, forexample, a magnetic on/off switch.

Other objects, advantages, and novel features of the present inventionwill become more fully apparent from the following detailed descriptionof the invention when considered in conjunction with the accompanyingdrawings, or may be learned by the practice of the invention as setforth herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention provides its benefits across a broad spectrum ofsecondary button cell battery technology. While the description whichfollows hereinafter is meant to be representative of a number of suchapplications, it is not exhaustive. As those skilled in the art willrecognize, the basic apparatus taught herein can be readily adapted tomany uses. This specification and the claims appended hereto should beaccorded a breadth in keeping with the scope and spirit of the inventionbeing disclosed despite what might appear to be limiting languageimposed by the requirements of referring to the specific examplesdisclosed.

Referring particularly to the drawings for the purposes of illustratingthe invention and its presently understood best mode only and notlimitation:

FIG. 1 is a plan view of one form of a button cell battery, whichincludes a radio frequency energy harvesting diode located in the gasketcleft and connected in parallel with the battery.

FIG. 2 is a cross-sectional view of the battery of FIG. 1 taken alongsection 2-2.

FIG. 3 is an enlarged cross-sectional view of the energy harvestingdiode assembly of the embodiment of FIG. 1.

FIG. 4 is as a diagrammatic schematic cross-sectional view of a radiofrequency transmitter recharging station adapted to recharging thebutton cell of the embodiment of FIG. 1.

FIG. 5 is a diagrammatic and schematic representation of a button cellin which an in situ recharging circuit is mounted in an electronicscompartment on the positive end of the cell.

FIG. 6 is a diagrammatic representation of an in situ recharging circuitadapted for mounting in the electronics compartment on the positive endof the button cell of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designateidentical or corresponding parts throughout the several views. It is tobe understood that the drawings are diagrammatic and schematicrepresentations of various embodiments of the invention, and are not tobe construed as limiting the invention in any way. The use of words andphrases herein with reference to specific embodiments is not intended tolimit the meanings of such words and phrases to those specificembodiments. Words and phrases herein are intended to have theirordinary meanings, unless a specific definition is set forth at lengthherein.

Referring particularly to the drawings, there is illustrated generallyat 10 a secondary battery having a button cell form wherein thechemistry is resiliently compressively enclosed within a resilientlydeformable case and separated by a flexibly configured separator.Certain features are illustrated out of proportion for the purposes ofillustration.

The resiliently deformable case (preferably, spring steel) is in twoparts, the first of which encloses the cathodic side and acts as acathodic terminal. The second part of the case encloses the anodic sideof the battery and acts as an anodic terminal. The cathodic side of thecase includes an annular side wall 12 integral with a generally circularplate 17 and a clamping rim 14. Clamping rim 14 is sealingly engagedwith an annular dielectric gasket element 18. Element 18 serves toelectrically insulated the anodic and cathodic battery case elementsfrom one another, and to sealingly retain the battery chemistry withinthe case. The anodic side of the battery case includes a truncatedconical section 20 integral with a circular pan 22. The larger end ofconical section 20 is formed into an annular seal engaging rim forpurposes of hermetically sealing with gasket 18. The generally annularspace (gasket cleft) between the anodic and cathodic sides holds thegasket element 18.

A corrugated separator member 32 has a generally circular or disk formand separates the anodic and cathodic compartments of the battery 10from one another, and serves the function of a conventional batteryseparator. The outer annular edge of separator 32 is sealed between casegasket 18 and inner seal 19. Separator 32 is preferably flexiblyconfigured, for example, by corrugations, so as to flexibly accommodatethe volumetric changes that are inherent in the battery chemistry duringthe discharge-recharge cycle of the battery. The material of theseparator may or may not be elastic, however, as flexibility may beprovided by the physical configuration of the separator.

The electro-chemical reactants that fill the anodic chamber of thebattery 10 are indicated at 34, and those that fill the cathodic chamberare indicated at 36. Most electricity producing chemical reactionsresult in a physical change in the volume of the respective reactants.Since the reactants are typically packed tightly into the battery case,this change in volume causes the case to swell during, for example, thedischarge phase of the discharge-recharge cycle. When the chemistry insuch a system is recharged the volume of the electrochemical reactantsshrinks. Conventional cases in prior primary button cells typically wereconstructed from soft steel that had very little resilience. Theswelling of the typical soft steel case during discharge was, therefore,not significantly reversible. As the reactants shrank during attemptedrecharging, the prior soft steel cases on primary button cell batteriesstayed distended or otherwise deformed. The volumetric change inducedcase deformation was largely permanent. Consequently, there was littleor no pressure on the reactants as soon as any significant reduction inthe volume of the reactants occurred. Electrical continuity within thebattery was degraded to the point where the battery became useless forits intended purpose. The migration of ions through the battery was alsoimpaired.

The case elements, according to the present invention are composed ofresiliently deformable material such as spring steel so that theydeflect resiliently without permanent deformation as the chemicalreactants swell and contract during the discharge-recharge cycle. Thisis illustrated in for example, FIG. 2. The nominal positions of therespective cathodic and anodic case elements are illustrated at 16 and22. The cathodic case element 16 enjoys a resilient excursion distancebetween a concave and convex configuration illustrated at 17. Theposition of the case element on the cathodic side at the limit of theconcave excursion is indicated at 28, and its position at the limit ofthe convex excursion is illustrated at 30. Likewise, the limits of theconcave and convex excursion of the case element 22 on the anodic sideof the case are illustrated at 24 and 26, respectively. The degree ofthese excursions is magnified in the drawings for the purposes ofillustration. During discharge the typical secondary battery chemistry,for example, swells and the resilient case elements 16 and 22 movetowards the convex configurations shown at 30 and 26, respectively. Whenthe secondary battery is fully recharged, the chemistry shrinks and thespringy case elements move towards the configuration shown at 28 and 24.As noted above, the battery separator 32 is corrugated so that it canflex to accommodate the above-described dimensional changes thataccompany the recharge-discharge cycle. The separator thus remainsintact from cycle to cycle. The magnitude of the corrugation ismagnified in the drawings for purposes of illustration. By resilientlyaccommodating the inevitable dimensional changes that occur during therecharge-discharge cycle, the anodic and cathodic reactants within thecell remain tightly apposed to each other across the flexible batteryseparator at all stages of the cycle.

The case is not permanently deformed as a result of the inherentvolumetric changes in the electrochemical reactants. By using resilientcase walls the need for extra compression members in the battery tomaintain the battery chemistry compressively confined in the case isavoided. The case can be composed of, for example, spring steel,beryllium-copper, metal loaded and other electrically conductiveengineering plastics, or the like. The entire case need no beconstructed of the same material. Various combinations of differentresiliently deformable electrically conductive materials can beincorporated at different locations in the case. The resilientdeformation need not be as indicated in FIG. 2, so long as the inherentvolumetric changes in the reactants is resiliently accommodated withoutsignificant permanent deformation of the case walls. It is not generallynecessary that the entire case be electrically conductive or resilient.The annular side wall can, for example, be composed of substantiallyrigid non-conductive material, if desired, provided the necessaryconductive paths are provided for the negative and positive sides. Arigid conductive material such as a conductive ceramic could be used forthe annular side wall, if desired. For the sake of efficientmanufacturing, each case element is typically made from a single pieceof material.

In a preferred embodiment, for example, a radio frequency (RF) energyharvesting diode is placed in parallel with the battery cell forrecharging purposes. The diode harvests energy from radio frequencyemissions. Preferably, the radio frequency emissions are generated undercontrolled conditions in a shielded charging station. Such a diodeassembly is indicated generally at 40. The diode 42 (FIG. 3) is placedin the annular gasket cleft between the positive and negative caseelements 20 and 14, respectively. The diode and associated circuitry canbe placed in the gasket itself or at the outer edge of the gasket solong as it is not shielded from the charging energy. This unpackaged rawdie is so small that it fits in the gasket cleft of a conventionalbutton cell. Thus, a full standard sized button cell battery form can beused for the cell. Cells of a standard height and diameter can be used.This maximizes the amount of the electrochemical reactants within thecell. The standard battery compartment in the appliance need not bemodified to accept cells configured according to the present invention.Standard production equipment and procedures can be used to make thecell, with only the added step of placing the diode assembly in theannular gasket cleft. Within the diode assembly 40, the diode 42 isencapsulated in, for example, a body of cured in situ epoxy 44. Anelectrically conductive path 46 is provided between the anodic side 20of the battery case and the diode. Likewise, an electrically conductivepath 48 is provided between the opposed side of the diode and thecathodic side 14 of the cell case. These electrically conductive pathscan be composed, for example, of an electrically conductive formed andcured in situ plastic, small wires, traces, or the like. For purposes ofillustration, only one diode assembly has been shown. As will be readilyunderstood by those skilled in the art, a plurality of two or more RFenergy harvesting diode assemblies can be used, if desired.

No special antenna is required for harvesting RF energy according to thepresent invention. The circuitry of an appliance such as, for example, aconventional hearing aid, and particularly the hearing aid audiotransducer and its typically direct connection to the positive terminalof the battery cell, as well as the battery case itself, can be used asthe antenna. No other antenna elements are absolutely required, althoughthey can be used, if desired.

With particular reference to FIG. 4, there is illustrated generally at50 a charging station, the principal components of which are two matingmetallic hemispheres 54 and 52, a radio frequency transmitter72, and amicrophone 76 that is operatively connected to transmitter 72.Hemispheres 52 and 54 are filled, for example, with reticulated foambeds 56 and 58, respectively, that are substantially transparent to RFenergy. The foam beds 56 and 58 serve to receive and hold appliances 60and 62 in recharging association with transmitter 72. Secondarybatteries 66 and 64 are operatively mounted within appliances 62 and 60,respectively. Radio frequency transmitter 72 is connected to a source ofenergy by, for example, electrical cord 74. Hemispheres 52 and 54 areadapted to move as indicated at 55 between an open configuration shownin FIG. 4 and a fully closed configuration wherein the exposed ends ofthe rechargingly associated appliances (for example, hearing aids) 60and 62 are received in foam pockets 68 and 70. Microphone 76 ispositioned close to and approximately equidistant from the appliances,particularly hearing aids, to pick up sounds emitted by the hearingaids.

In its simplest form as applied to hearing aid appliances, therecharging station 50 consists of a platform onto which the hearing aidsare placed. An energy source, for example, an RF transmitter is providedthat emits RF energy of, for example, approximately 0.2 to 2 wattshaving a frequency of, for example, approximately 2.4 to 5.8 gigahertz(GHz). RF emissions can most effectively recharge the secondary cellswhen the platform is covered by an RF shield/dome reflector. In this wayno RF energy escapes form the recharging station and further, thereflector focuses the RF energy onto the hearing aids. The RFtransmitter 72 should also be fully shielded to protect any appliancessuch as radios, pace makers, and the like, from interference. Typically,a safety switch or interlock is provided (not shown) that prevents theRF transmitter from being activated unless the transmitter is fullyshielded. Feedback control of the charging cycle can be efficientlydesigned into the recharging station 50, for example, by using acousticsignaling from the hearing aids 60 and 62 to indicate the level ofcharge on the batteries. This is accomplished by modulating the RFfrequency with a low frequency signal and the use of an inexpensivemicrophone 76 situated near the hearing aids 60 and 62. The hearing aids60 and 62 are left on during recharging so that they emit a sound. Thecharacteristics of the tone change as the degree of charge in the cellchanges. These changes in the characteristics of the tone emitted by theunmounted hearing aid can be employed to protect the battery fromovercharging. A charge control member can thus control (between themaximum capacity of the RF transmitter, and completely off) the amountof radio frequency energy that is generated by the charging stationresponsive to the level of electrical charge on the secondary cell. TheRF energy harvesting diode, see, for example, 42, and more particularly,it's relationship to the hearing aid battery may obviate the need to useadditional regulating or switch means such as, for example, a zenerdiode, a MOSFET switch, or the like (not shown). The energy harvestingdiode 42 is, for example, wired in parallel, see 46 and 48, with thebattery, see, for example, 10 or 64. As will be understood by thoseskilled in the art, the use of a plurality of energy harvesting diodesin the gasket cleft permits their configuration into serial or parallelarrangements, or both, (not shown) to multiply the voltage or thecurrent, or both. When the hearing aid is in the recharging station andis left “on” during recharging, the hearing aid itself bleeds off someof the charging current and converts it into an audible signal. As thebattery voltage increases, more current is automatically consumed by thehearing aid circuit (generally according to ohms law). This circuit, ineffect, acts as a “taper charger.” When the battery is low(substantially discharged), less current is used by the hearing aidcircuit, and as the battery becomes progressively more charged, thehearing aid progressively uses more of the current. As the hearing aiduses more current, it's acoustic emissions become louder which in turnare detected by the charging station through it's microphone pickup, forexample, 76. When the battery is fully charged (it's charge acceptancedecreases substantially) the amplitude of the acoustic emissions willincrease more rapidly (the derivative of sound intensity over time).This can be used as the signal for the charge control member of thecharging station to lower or discontinue the RF output. The use ofacoustic signals to activate the charge control system is particularlyuseful when a single charging element, such as one or more energyharvesting diodes, is used. This allows for a very simple one activecomponent charging system in the battery-appliance combination, with thecomplexity involved with charge control being located in the rechargingstation.

Energy harvesting diodes can also charge batteries from other energysources, such as, for example, by acting as photovoltaic cells andharvesting photo energy. This requires that the diode be exposed tolight of the appropriate wavelength, for example, ultraviolet, toactivate the diode. The battery compartment must either be at leastpartly transparent to the light energy that is to be harvested, or thediode that is associated with the battery must be directly exposed tothe light. When the control circuitry controllingly associated with RFtransmitter 72 recognizes that the microphone 76 has detected a tonewith certain predefined characteristics that are associated with a fullycharged cell, the charge control circuitry shuts off the RF transmitterand, for example, turns on a signaling LED (not shown) indicating thatthe hearing aid battery is recharged.

With particular reference to FIGS. 5 and 6, there is indicated generallyat 80 a specially constructed secondary button cell battery in which thesecondary battery chemistry is confined within section 82, and an insitu charging circuit is confined in a recharging section 84 on thepositive side of the cell. A typical in situ recharging circuit that issuitable for use in compartment 84 is illustrated at 86. The in siturecharging circuit 86 is essentially composed of a voltage doublingrectifier circuit and P-channel depletion type mosfet with a low gatevoltage and a low on resistance. All of these components are containedwithin the electronics compartment 84 of the battery. When exposed toradio frequency (RF) energy of the appropriate frequency and intensity,the hearing aid transducer inductive coil (contained within the hearingaid transducer 88) acts as an inductively loaded RF antenna and is inresonance with capacitor 92. The system is grounded at 104. The RFenergy detector circuit (that is, the recharging circuit) composed ofcapacitors 92 and 100, and diodes 96 and 98 rectifies and doubles the RFvoltage. The rectified current then flows into the battery 102 acrossdiode 94, thus recharging the battery. In addition, the gate of theP-channel depletion type mosfet 90 is charged through 98 and thus turnsoff. By so doing, the hearing aid is automatically turned off, thuspreserving energy while in the charging mode. When the RF rechargingenergy is turned off (for example, when the hearing aid is removed fromthe recharging stand) the mosfet gate is no longer charged through diode98 and in addition, rectification by diode 94 disallows current from thebattery to charge the mosfet gate. When the mosfet's gate is no longercharged, the mosfet 90 becomes conductive and thus turns the hearing aidback on.

Battery charge control can be achieved in several different ways inaddition to the audio signaling described above. A zener diodecontrollingly associated with a circuit such as that illustrated in FIG.6 can server to prevent overcharging of the cell. When a cell is fullyrecharged, sufficient current is released across a zener diode (notshown), which bypasses the mosfet and turns on the associated appliance.In an embodiment where an energy harvesting diode is present in a gasketcleft, the energy harvesting diode and zener diode can be positioned inseries with the battery. When the charge on the cell reaches apredetermined level, the zener diode cuts of the supply of harvestedenergy to the cell. A radio frequency identification (RFID) transmittercan be associated with the cell, particularly in the battery compartmentof an appliance, so as to transmit an indication of the level of thecharge on the cell to the RF generator for appropriate predeterminedresponse by the charge controlling member. An RFID tag can also be usedas an energy harvester. The degree of the resilient deformation of thecell case walls can be monitored and used as a controlling indication ofthe level of charge on the secondary cell. A micro current OP AMPcircuit can be employed to control charging. The charge control cansense or rely on the direct sensing of the level of charge on the cell,or it can indirectly sense or rely on the indirect sensing of the chargelevel for control purposes.

For purposes of convenience, a pocket sized cell charging station can beprovided. For example, an energy harvesting diode-zener diode and mosfetoff switch can be provided to allow a hearing aid to be turned off whenexposed to an RF signal. The RF signal generator and charger can beeasily incorporated into a pocket travel case to automatically turn offthe hearing aid in the field. Also, such a traveling case for theappliance can include a magnetic switch activation element designed tocooperate with a magnetically actuated switch member in the appliance.Thus, for example, putting the appliance in the traveling case causesthe magnetic field in the case to activate the switch in the applianceso as to turn the appliance off. Other switch members are conventionallyavailable and well known to those skilled in the art.

Radio frequency generators of various designs and capacities areconventionally available, as is well known to those skilled in the art.For example, inexpensive tiny 2.4 and 5.8 gigahertz (GHz) single chip RFtransmitters/receivers suitable for use as charging station electronicsare conventionally available.

The dielectric gasket element is, for example, composed of conventionalgasket material, or of specially designed material. Where energyharvesting diodes are employed, they can be embedded in the gasketduring its manufacture together with the desired electrical conductors,or inserted into the gasket cleft after the gasket is in place, asdesired.

A variety of energy harvesting diodes can be used, including those thatare used for RF detection, such as 1N34A germanium diode.

What have been described are preferred embodiments in whichmodifications and changes may be made without departing from the spiritand scope of the accompanying claims. Many modifications and variationsof the present invention are possible in light of the above teachings.It is therefore to be understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed.

1. A secondary battery in the form of a button cell, said secondarybattery comprising: a positive case element; a negative case element,said positive and negative case elements being spaced from one anotherby a gasket cleft; a dielectric gasket element sealingly andelectrically insulatively positioned in said gasket cleft; asubstantially sealed battery chamber bounded by said positive andnegative case elements and substantially sealed by said dielectricgasket element; and a diode chargingly associated with said secondarybattery, said diode being adapted to harvesting at least radio frequencyenergy and chargingly supplying such harvested energy to said secondarybattery.
 2. A secondary battery of claim 1 wherein said diode ispositioned in said gasket cleft.
 3. A secondary battery of claim 1including a plurality of said diodes.
 4. A secondary battery of claim 1wherein said diode is connected in parallel with said secondary battery.5. A secondary battery of claim 1 wherein said diode is also adapted toharvesting photo energy.
 6. A secondary battery in the form of a buttoncell, said secondary battery comprising: a positive case element; anegative case element, said positive and negative case elements beingspaced from one another and defining a gasket cleft therebetween; adielectric gasket element sealingly and electrically insulativelypositioned in said gasket cleft; a substantially sealed battery chamberbounded by said positive and negative case elements and substantiallysealed by said dielectric gasket element; and secondary batterychemistry compressively confined in said battery chamber and adapted toundergoing a plurality of discharge-recharge cycles, said secondarybattery chemistry being adapted to inherently undergoing volumetricchange during a said discharge-recharge cycle, said secondary batterybeing adapted to maintaining said secondary battery chemistrycompressively confined in said battery chamber substantially throughouta plurality of said discharge-recharge cycles.
 7. A secondary battery ofclaim 6 wherein said positive and negative case elements aresufficiently resilient to accommodate said volumetric change withoutsuffering permanent deformation.
 8. A secondary battery of claim 6wherein said secondary battery chemistry includes at least two reactantsseparated by a flexibly configured separator, said flexibly configuredseparator being adapted to flexibly accommodate said volumetric change.9.-11. (canceled)
 12. A secondary battery in the form of a button cell,said secondary battery comprising: a positive case element; a negativecase element, said positive and negative case elements being spaced fromone another to define a gasket cleft therebetween; a dielectric gasketelement sealingly and electrically insulatively positioned in saidgasket cleft to form a substantially sealed battery chamber bounded bysaid positive and negative case elements and substantially sealed bysaid dielectric gasket element; a diode chargingly associated with saidsecondary battery, said diode being adapted to harvesting at least radiofrequency energy and chargingly supplying such harvested energy to saidsecondary battery; and secondary battery chemistry compressivelyconfined in said battery chamber and adapted to undergoing a pluralityof discharge-recharge cycles, said secondary battery chemistry beingadapted to inherently undergoing volumetric change during a saiddischarge-recharge cycle, said secondary battery being adapted tomaintaining said secondary battery chemistry compressively confined insaid battery chamber substantially throughout a plurality of saiddischarge-recharge cycles. 13.-15. (canceled)